Apple's New Migration Feature
This week iOS 12.4 was released and within this update, Apple implemented a new feature which allows iPhone to iPhone data migration.
Now, what this means is that now when you want to transfer data from one device to the other you don't have to rely on using iCloud to redownload it all.
With a new device, once your Apple ID has been confirmed, quick start uses the device's camera to scan an animation to pair them both. From here you'll have the standard set up of Touch ID and Face ID and it will then prompt the new "Transfer from Phone" option.
Even though it's a faster and quicker way of data transfer in comparison to iCloud, it is still dependent as it is based on what/how much you have on the existing iPhone.
For this feature to work, it requires both devices to be on the new iOS12.4 or later. As any devices that are on earlier versions of iOS 12 won't be supported.
Image - Apple.com